1. Technical Field
The present invention relates to projection televisions and, in particular, to burnout imprinting protection. Still more particularly, the present invention provides a method and apparatus for dynamic burnout imprinting protection with shift correction.
2. Description of Related Art
Televisions are available in two popular screen formats. The standard format has a 4:3 aspect ratio, meaning the screen is four units wide and 3 units high. In contrast, the common widescreen format has a 16:9 aspect ratio, which is wider than the standard format. Due to the two common aspect ratios, visual media is also typically available in standard or widescreen format.
However, many times visual media is only available in one format. If the screen aspect ratio does not match the media format, the content is displayed on a portion of the screen. Typically, the remainder of the screen is filled in with a solid color, such as black. Black is a special color. In some projectors, such as cathode ray tubes, black means that nothing is being projected in that area. In other projectors, black is a projection composed of multiple colors which simulate black. Thus, for example, a widescreen format presentation displayed on a standard screen may have black bars on the top and bottom of the screen. Conversely, a standard format presentation displayed on a widescreen format television may have black bars on the left and right sides of the screen.
Due to the length of time a non-matching media is displayed on a screen, the screen may experience burnout imprinting. In most cases, burnout imprinting results in the area that is blacked out being noticeably brighter than the remainder of the screen real estate. In other cases, burnout imprinting results in the area that is blacked out being noticeably darker. In the case of a cathode ray tube (CRT) television, burnout imprinting affects the tube. Projection televisions typically have three guns: red, green, and blue. These guns then project the image onto a screen. In most cases, the screen material is not susceptible to imprint burning. With projection televisions, burnout imprinting is likely to affect the projection guns and, to a lesser extent, the projector lenses.
Therefore, it would be advantageous to provide improved burnout imprinting protection on projection televisions.